论文标题
受约束量子系统中的新兴示踪动力学
Emergent tracer dynamics in constrained quantum systems
论文作者
论文摘要
我们展示了标记,可区分的颗粒的示踪剂运动如何有效地描述具有约束的各种同质量子多体系统中的传输。我们考虑在受约束自旋相互作用的一维晶格上的跨粒子系统,以使粒子形成的有效旋转模式的某些或所有多极矩得到保守。一方面,当所有瞬间(以及整个旋转模式)都是保守的时,动态自旋相关性降低到示踪剂运动相同,通常会产生一个亚延伸的动力学指数$ z = 4 $。这提供了一个共同的框架,以了解几种约束晶格模型的动态,包括具有XNOR或$ TJ_Z $ - 约束的模型。我们考虑具有如此保守的自旋模式的随机统一电路动力学,并使用示踪剂图片获得其延迟动态相关性的精确表达式。我们的结果也可以扩展到具有保守的自旋图案但动力学对模式不敏感的可集成量子多体系统,其中包括折叠的XXZ自旋链。另一方面,当仅保守图案的矩时数量有限的矩时,动力学将通过具有示踪剂分布函数的自旋模式的内部流体动力学卷积来描述。结果,我们发现示踪剂通用性在通用系统中至少保持了图案的四极力矩的保守。如果只有模式的总磁化和偶极矩是恒定的,那么我们发现了具有相等动力学指数但不同缩放函数的两个过程的有趣共存,这与一阶转变中的相共存有关。
We show how the tracer motion of tagged, distinguishable particles can effectively describe transport in various homogeneous quantum many-body systems with constraints. We consider systems of spinful particles on a one-dimensional lattice subjected to constrained spin interactions, such that some or even all multipole moments of the effective spin pattern formed by the particles are conserved. On the one hand, when all moments - and thus the entire spin pattern - are conserved, dynamical spin correlations reduce to tracer motion identically, generically yielding a subdiffusive dynamical exponent $z=4$. This provides a common framework to understand the dynamics of several constrained lattice models, including models with XNOR or $tJ_z$ - constraints. We consider random unitary circuit dynamics with such a conserved spin pattern and use the tracer picture to obtain exact expressions for their late-time dynamical correlations. Our results can also be extended to integrable quantum many-body systems that feature a conserved spin pattern but whose dynamics is insensitive to the pattern, which includes for example the folded XXZ spin chain. On the other hand, when only a finite number of moments of the pattern are conserved, the dynamics is described by a convolution of the internal hydrodynamics of the spin pattern with a tracer distribution function. As a consequence, we find that the tracer universality is robust in generic systems if at least the quadrupole moment of the pattern remains conserved. In cases where only total magnetization and dipole moment of the pattern are constant, we uncover an intriguing coexistence of two processes with equal dynamical exponent but different scaling functions, which we relate to phase coexistence at a first order transition.